Triangular Cavity Research Articles

Flow boiling of R134a and HFE-7000 in a single silicon microchannel with microstructured sidewalls

Flow boiling heat transfer is investigated in a single silicon microchannel with microstructured sidewalls using R134a (at 0.19 reduced pressure) and HFE-7000 (at 0.035 reduced pressure) as working fluids. The channel is 51 mm long with a 400 μm x 400 μm square cross section. Sidewall microstructures in the form of triangular cavities for the entire height of the channel were introduced during the fabrication process. By including the cavity pattern in the photolithography mask design, high accuracy and reproducibility is ensured during the fabrication of the test sample. A smooth channel with the same geometry but without sidewall microstructures was also fabricated. Flow boiling experimental results are presented for both channel configurations. For R134a at mass velocity G = 800 kg m−2 s−1, the comparison of the boiling curves shows that: in the channel with the microstructures, the wall superheat at the onset of nucleate boiling (ONB) is reduced from 21 K to 6 K as compared to the smooth channel. An increase of the flow boiling heat transfer coefficient up to 40% is found in the microstructured channel, which must be due to the increased number of active nucleation sites. Heat transfer results, flow visualizations and comparison between R134a and HFE-7000 data provide a clearly evidence of the active role of bubble nucleation during flow boiling in microchannels. These results are of fundamental importance in the design of next generation thermal management systems for electronics.

Numerical investigation of the effect of triangular cavity on the unsteady aerodynamics of NACA 0012 at a low Reynolds number

Time accurate numerical simulations were conducted to investigate the effect of triangular cavities on the unsteady aerodynamic characteristics of NACA 0012 airfoil at a Reynolds number of 50,000. Right-angled triangular cavities are placed at 10%, 25% and 50% chord location on the suction and have depths of 0.025c and 0.05c, measured normal to the surface of the airfoil. The second-order accurate solution to the RANS equations is obtained using a pressure-based finite volume solver with a four-equation transition turbulence model, γ–Re θt, to model the effect of turbulence. The two-dimensional results suggest that the cavity of depth 0.025c at 10% chord improves the aerodynamic efficiency ( l/d ratio) by 52%, at an angle of attack of α = 8°, wherein the flow is steady. The shallower triangular cavity when placed at 25%c and 50%c enhances the l/d ratio by only 10% and 17%, respectively, in the steady-state regime of angles of attack between α = 6° and 10°. The deeper cavity also enhances the l/d ratio by up to 13%, 22% and 14% at angles of attack between α = 6° and 10°. Even in the unsteady vortex shedding regime, at α =12° and higher, significant improvements in the time-averaged l/d ratios are observed for both cavity depths. The improvements in l/d ratio in the steady-state, pre-stall regime are primarily because of drag reduction while in the post-stall, unsteady regime, the improvements are because of enhancements in time-averaged C l values. The current finding can thus be used to enhance the aerodynamic performance of MAVs and UAVs that fly at low Reynolds numbers.

Quantum photonics in triangular-cross-section nanodevices in silicon carbide

Silicon carbide is evolving as a prominent solid-state platform for the realization of quantum information processing hardware. Angle-etched nanodevices are emerging as a solution to photonic integration in bulk substrates where color centers are best defined. We model triangular cross-section waveguides and photonic crystal cavities using Finite-Difference Time-Domain and Finite-Difference Eigensolver approaches. We analyze optimal color center positioning within the modes of these devices and provide estimates on achievable Purcell enhancement in nanocavities with applications in quantum communications. Using open quantum system modeling, we explore emitter-cavity interactions of multiple non-identical color centers coupled to both a single cavity and a photonic crystal molecule in SiC. We observe polariton and subradiant state formation in the cavity-protected regime of cavity quantum electrodynamics applicable in quantum simulation.

Designing of microsink to maximize the thermal performance and minimize the Entropy generation with the role of flow structures

Designing a novel microsink with geometric structures for better cooling of compact tiny-sized electronic devices at lower pressure drop is the utmost desire of recent technological development. A three-dimensional numerical study of conjugate heat transfer has been carried out to propose a microsink with the disruptive structures placed symmetrically about the vertical midplane in a rectangular microchannel. The channels are made of silicon with the structures like triangular cavity (TC), secondary branches (SB) and blockage (B) with water as a working fluid. The effects of these structures are illustrated by heat transfer, friction factor, thermal performance (TP), entropy generation (EG) due to heat transfer, entropy generation (EG) due to pressure drop and entropy generation number (EGN) over the range of Reynolds number (Re) from 146 to 618. The best channel has been identified from the rigorous analysis among the microchannels with the only triangular cavity (TC), triangular cavity with the secondary branch (TCSB) and triangular cavity along with secondary branch and blockage (TCSBB) from the highest TP and minimum EGN. These two models have been chosen to find out a best channel as criteria of highest heat transfer with the same pumping power from the highest TP and minimum temperature of electronic sink from the lowest EGN. The highest TP and lowest EGN are obtained from the channel TCSBB compared to other three channels. The parametric variation of relative angle of the secondary branch, length of cavity, width of secondary branch and cavity, pitch distance have been varied to find the maximum TP and the minimum EGN. The values have been obtained equal to 2.01 and 0.41 respectively at Re of 480. The significant roles of longitudinal vortex on the augmentation of heat transfer and minimizations of EG mechanism with the alteration of geometrical parameters are exploited and described explicitly. Finally, the correlations of heat transfer enhancement and rise in pressure drop dependent on geometric parameter have been inscribed based on Response surface methodology.

Magnetic field effects on melting and solidification of PCMs in an isosceles triangular cavity

Magnetic field effects on melting and solidification of PCMs in an isosceles triangular cavity

Space- and time-resolved second harmonic spectroscopy of coupled plasmonic nanocavities

Abstract Localized surface plasmon resonances of individual sub-wavelength cavities milled in metallic films can couple to each other to form a collective behavior. This coupling leads to a delocalization of the plasmon field at the film surface and drastically alters both the linear and nonlinear optical properties of the sample. In periodic arrays of nanocavities, the coupling results in the formation of propagating surface plasmon polaritons (SPP), eigenmodes extending across the array. When artificially introducing dislocations, defects and imperfections, multiple scattering of these SPP modes can lead to hot-spot formation, intense and spatially confined fluctuations of the local plasmonic field within the array. Here, we study the underlying coupling effects by probing plasmonic modes in well-defined individual triangular dimer cavities and in arrays of triangular cavities with and without artificial defects. Nonlinear confocal spectro-microscopy is employed to map the second harmonic (SH) radiation from these systems. Pronounced spatial localization of the SPP field and significant enhancements of the SH intensity in certain, randomly distributed hot spots by more than an order of magnitude are observed from the triangular arrays as compared to a bare silver film by introducing a finite degree of disorder into the array structure. Hot-spot formation and the resulting enhancement of the nonlinear efficiency are correlated with an increase in the lifetime of the localized SPP modes. By using interferometric SH autocorrelation measurements, we reveal lifetimes of hot-spot resonances in disordered arrays that are much longer than the few-femtosecond lifetimes of the localized surface plasmon resonances of individual nanocavity dimers. This suggests that hot spot lifetime engineering provides a path for manipulating the linear and nonlinear optical properties of nanosystems by jointly exploiting coherent couplings and tailored disorder.

Exceptional Cocatalyst-Free Photo-Enhanced Piezocatalytic Hydrogen Evolution of Carbon Nitride Nanosheets from Strong In-Plane Polarization.

Utilizing mechanical energy to produce hydrogen is emerging as a promising way to generate renewable energy, but is challenged by low efficiency and scanty cognition. In this work, graphitic carbon nitride (g-C3 N4 ) with an atomically thin sheet-like structure is applied for prominent piezocatalytic and photo-enhanced piezocatalytic H2 production. It is revealed that the anomalous piezoelectricity in g-C3 N4 originates from the strong in-plane polarization along the a-axis, contributed by the superimposed polar tri-s-triazine units and flexoelectric effect derived from the structured triangular cavities, which provides powerful electrochemical driving force for the water reduction reaction. Furthermore, the photo-enhanced charge transfer enables g-C3 N4 nanosheets to reserve more energized polarization charges to fully participate in the reaction at the surface reactive sites enriched by strain-induced carbon vacancies. Without any cocatalysts, an exceptional photo-piezocatalytic H2 evolution rate of 12.16 mmol g-1 h-1 is delivered by the g-C3 N4 nanosheets, far exceeding that of previously reported piezocatalysts and g-C3 N4 photocatalysts. Further, high pure-water-splitting performance with production of the value-added oxidation product H2 O2 via photo-piezocatalysis is also disclosed. This work not only exposes the potential of g-C3 N4 as a piezo-semiconductor for catalytic H2 evolution, but also breaks a new ground for the conversion of solar and mechanical energy by photomediated piezocatalytic reaction.

Effect of geometric cavity shape and diameter on mechanical properties of water lubricated hydrostatic stern bearing

In order to improve the working condition of low speed, the stern bearing friction caused by poor lubrication of abnormal vibration and noise problem, this paper starts from the influence of problem, takes the circular, elliptical, square, I-shaped and triangular cavity as the research object, establishes the water lubricated stern bearing model, and carries on the mechanical analysis of the model by using ANSYS/Workbench; and on this basis, study the effect of the diameter of the cavity on the mechanical properties of stern bearing. The results show that the displacement, strain and stress of circular cavity bearing are better than other geometric cavity bearings. Among them, the mechanical properties of 3∼4mm have a better performance.

Thermal performance analysis of multi-objective optimized microchannels with triangular cavity and rib based on field synergy principle

In our previous work, a new structure of a microchannel with triangular cavity and rib was proposed to enhance heat transfer. To obtain excellent thermal performance, a multi-objective optimization using Response Surface Methodology (RSM), Non-dominated Sorting Genetic Algorithm (NSGA-II), and k-mean clustering was performed to obtain a Pareto front. Thirty sets of numerical data were used to optimize design variables (cavity height, rib height, and Reynold number) of objective functions (thermal resistance Rth and pumping power PP). Results showed that compared heat transfer amount in the process, convective heat transfer is the dominant part than heat conduction and heat loss. Four representative solutions obtained by k-means clustering divided the Pareto front into five regions, and the moderate Rth and PP resulted into the best heat transfer characteristics. Temperature difference between fluid and heating wall decreased from 26 K, obtained for the rectangular microchannel, to 17 K, obtained for the optimized one. The best thermal performance of Case 4 (e1 = 0.0572 mm, e2 = 0.0224 mm) was obtained for a thermal enhanced factor of 1.2305 due to good synergy between the velocity field and temperature gradient. Therefore, rational structural designs efficiently improve heat removal ability in limited heat exchange area.

New approach for T-shaped uterus: Metroplasty with resection of lateral fibromuscular tissue using a 15 Fr miniresectoscope. A step-by-step technique.

T-shaped uterus is a congenital uterine malformation (CUM), only recently defined by the ESGE ESHRE classification as Class U1a. The uterus is characterised by a narrow uterine cavity due to thickened lateral walls with a correlation 2/3 uterine corpus and 1/3 cervix. Although the significance of this dysmorphic malformation on reproductive performance has been questioned, recent studies reported significant improvement of life birth rates after surgical correction in patients with failed in-vitro fertilisation (IVF) or recurrent miscarriage. The classical surgical technique to treat a T-shaped uterus is by performing a sidewall incision with the micro scissor or bipolar needle, resulting in a triangular cavity.In this video article, we describe a new surgical technique with a step-by-step method combining three- dimensional ultrasound (3D-US) and hysteroscopic metroplasty in an office setting, using a 15 Fr office resectoscope (Karl Storz, Tuttlingen, Germany), to treat a T-shaped uterus by resecting the lateral fibromuscular tissue of the uterine walls. No complications occurred and the postoperative hysteroscopy showed a triangular and symmetrical uterine cavity without any adhesions.

New approach for T-shaped uterus: Metroplasty with resection of lateral fibromuscular tissue using a 15 Fr miniresectoscope. A step-by-step technique.

T-shaped uterus is a congenital uterine malformation (CUM), only recently defined by the ESGE ESHRE classification as Class U1a. The uterus is characterised by a narrow uterine cavity due to thickened lateral walls with a correlation 2/3 uterine corpus and 1/3 cervix (Grimbizis et al, 2013). Although the significance of this dysmorphic malformation on reproductive performance has been questioned, recent studies reported significant improvement of life birth rates after surgical correction in patients with failed in-vitro fertilisation (IVF) or recurrent miscarriage (Ferro et al, 2018; Di Spiezio Sardo et al, 2020; Alonso Pacheco et al. 2019). The classical surgical technique to treat a T-shaped uterus is by performing a sidewall incision with the micro scissor or bipolar needle, resulting in a triangular cavity. In this video article, we describe a new surgical technique with a step-by-step method combining three-dimensional ultrasound (3D-US) and hysteroscopic metroplasty in an office setting, using a 15 Fr office resectoscope (Karl Storz, Tuttlingen, Germany), to treat a T-shaped uterus by resecting the lateral fibromuscular tissue of the uterine walls. No complications occurred and the postoperative hysteroscopy showed a triangular and symmetrical uterine cavity without any adhesions.

Graphdiyne oxide and graphene oxide sense monovalent cations differently: The alkyne and alkene physicochemistry

Abstract The differences between graphdiyne oxide (GDYO) and graphene oxide (GO) in physicochemistry and functionalities are important for precisely selecting the most suitable carbon allotrope for specific proposes, and essential for our understanding of alkyne and alkene fundamentals. However, the precise distinctions between GDYO and GO in ion sieving and sensing are basically unknown. Here we show that GDYO senses monovalent cations differently from GO. The unique sp-hybridization in GDYO provides it with more affinity with H2O molecules and stronger Coulomb electrostatic repulsion to maintain zeta potential high enough to preserve its interfacial colloidal stability without changes in attachment kinetics in the presence of Na+ and K+. Na+ and K+ freely move through the rotatable triangular cavities of GDYO. By comparison, GO shows less H2O affinity and zeta potential. Colloidal GO aggregates with Na+ and K+. Both GO and GDYO sense concentration changes of bivalent and trivalent ions, resulting in interfacial instability that reaches zeta potential plateaus within narrow lower ion concentrations due to electrostatic force and van der Waals force. The present study discovers characteristics of GDYO sp-hybridization and its role in sensing monovalent cations, and elucidates physicochemical differences between GDYO and GO in sensing ions.

Numerical study of energy transmission through copper-based nanofluid contained in a partially heated isosceles triangular cavity in the presence of heat source/sink

This study reports computational simulation of natural convective energy transport through copper-based nanofluid contained in partially heated isosceles triangular conduit in the presence of invariable magnetic field under the influence of energy source/sink. Inclined sides of the enclosure are retained cold and horizontal boundary is supposed thermally insulated. Heat source of a particular length is placed on the horizontal wall. Relations expressing the energy transport and fluid flow are first dealt by penalty scheme and then composed expressions are assembled through Galerkin approximation scheme. Pertinent physical parameters governing the flow are the solid volume increment of nanoparticles (0.0 < < 0.06), Hartmann number (0 < Ha < 100), Rayleigh number (105 < Ra < 108) and coefficient of heat source/sink (−10 < Q < 10). It has been noted through this investigation that in consequence of magnetic force, reduction in heat transport occurs. Conduction and convection regimes are dominant for small and large Rayleigh numbers respectively. Energy transport rate is found zero on corners of the cold inclined walls. Obtained computational results reveal that the flow pattern relies considerably on the concentration of nanoparticles, coefficient of energy source/sink, Rayleigh and Hartmann numbers. Computed solutions are expressed through plots of streamlines, isothermal lines, and rate of local and overall energy flow. The current results are also validated through graphical comparison with the existing literature.

Impact of a closed space rectangular heat source on natural convective flow through triangular cavity

In the existing numerical analysis is developed to impact of a closed space rectangular heat source on natural convective flow-through triangular cavity. The present problem is expressed as non-linear governing equations extended mathematical model is solved by engaging a Galerkin weighted residual process of a finite element scheme. Some investigation is acted for several Rayleigh number (Ra) at Pr = 0.71 on flow pattern and heat variation inside an enclosure. The resulting numerical clarifications of the query are exhibited graphically in phases of streamlines, velocity profiles, isotherms, Rectangular bar effectiveness, mean Nusselt number, and average fluid temperature. The acquired outcomes verified that a rate of heat variation progress with the rise of a Rayleigh number within a triangular cavity. Results are verified relating to a published work.

Numerical simulation of mixed convection flow and heat transfer in the lid-driven triangular cavity with different obstacle configurations

There are several industrial applications, particularly lid-driven walls, for mixed convection heat transfer characteristics across various cavities. In order to increase the effectiveness of cooling, electrical, electronic and nuclear devices and to monitor the fluid flow and heat exchange of solar thermal installations and thermal storage, such a problem requires further investigation. The main goal of this profound study is to examine the convective heat transfer nature of thermal convection on Newtonian MHD fluid in a lid-driven triangular cavity subjected to heating by a thick triangular wall, including the effects of varying Richardson number, Reynolds number, Hartmann number, and cold circular obstacle. Graphical illustration shows that the upper wall having temperature Th is moving from left to right, whereas inclined sidewalls are adiabatic. Further, a cold circular obstacle containing temperature T∗∗ is placed near the left and right wall of the triangular cavity with T∗∗ < Th. The governing flow equations are tackled by the Galerkin Finite Element Method (GFEM) to prepare the desired results. Velocity contours, isotherms and heat transfer rates demonstrate flow kinematics and heat transport processes. The high estimate of the Reynolds number has been found to provide a decent rate of convective heat transfer to a good liquid progression. For a higher number of Grashof, which achieves the maximum convection intensity, it is checked that natural convection dominates within the convection system. The Richardson number is a rising function of the Nusselt number, while the opposite trend is observed due to the rise in the Hartmann number.

Numerical solution strategy for natural convection problems in a triangular cavity using a direct meshless local Petrov-Galerkin method combined with an implicit artificial-compressibility model

Thermal analysis of natural convection in a cavity is solved by numerical approach. The direct meshless local Petrov–Galerkin method combined with an implicit artificial-compressibility model is proposed here to simulate laminar natural convective heat transfer in triangular cavities. The spatial terms of the governing equation are discretized using the direct meshless local Petrov–Galerkin method with the Dirac function as the test function. The method uses an artificial-compressibility scheme to couple the pressure with the velocity components directly. The semi-algebraic system is solved using an implicit backward Euler pseudo-time method. Kovasznay flow problem is presented to examine the accuracy of proposed method. The validation of the obtained results by using experimental data is also provided, and four test problems — natural convection in an equilateral triangular cavity, a right-angled triangular cavity, an isosceles triangular cavity, and an irregular triangular cavity — are solved by using the proposed method. The numerical results obtained using the proposed method showed excellent agreement with those obtained using the conventional methods available in the literature.

Dissipation-induced antiferromagneticlike frustration in coupled photonic resonators

We propose a photonic quantum simulator for anti-ferromagnetic spin systems based on reservoir engineering. We consider a scheme where quadratically driven dissipative Kerr cavities are indirectly coupled via lossy ancillary cavities. We show that the ancillary cavities can produce an effective dissipative and Hamiltonian anti-ferromagnetic-like coupling between the cavities. By solving the master equation for a triangular cavity configuration, we demonstrate that the non-equilibrium steady state of the system bears full analogy with the ground state of an antiferromagnetic Ising model, exhibiting key signatures of frustration. We show that when the effective photon hopping amplitude is zero, the engineered non-local dissipation alone is capable of inducing antiferromagnetic interaction and frustration. This simple scheme can be generalised to arbitrary lattice geometries, providing a fully controllable recipe for simulating antiferromagnetism and frustration on a controlled quantum optical platform.

Higher-order Hermite-Gauss modes for gravitational waves detection

As part of the research on thermal noise reduction in gravitational-wave detectors, we experimentally demonstrate the conversion of a fundamental ${\mathrm{TEM}}_{00}$ laser mode at 1064 nm to higher-order Hermite-Gaussian modes (HG) of arbitrary order via a commercially available liquid crystal spatial light modulator. We particularly studied the ${\mathrm{HG}}_{5,5}/{\mathrm{HG}}_{10,10}/{\mathrm{HG}}_{15,15}$ modes. A two-mirror plano-spherical cavity filters the higher-order modes spatially. We analyze the cleaned modes via a three-mirror diagnosis cavity and measure a mode purity of $96/93/78%$ and a conversion efficiency of $6.6%/3.7%/1.7%$, respectively. A full set of simulations and mathematical proofs are also presented which shows that (i) Hermite-Gauss modes resonate in a two-mirror cavity provided mirrors are properly angled with respect to the impinging mode, and (ii) Hermite-Gauss modes resonate in triangular cavities. Hence, higher-order Hermite-Gauss modes are compatible with ground-based gravitational-wave detectors' architecture and can be employed for the mitigation of mirror thermal noise for the third generation Einstein Telescope or Cosmic Explorer.

Single‐ and triple‐band bandpass filters using novel perturbed isosceles right‐angled triangular SIW cavities

Single‐ and triple‐band bandpass filters using novel perturbed isosceles right‐angled triangular SIW cavities

Effects of radiative heat flux and heat generation on magnetohydodynamics natural convection flow of nanofluid inside a porous triangular cavity with thermal boundary conditions

AbstractWhen the nanoparticles are incorporated into the base fluid, the resultant fluid is known as nanofluid. Nanofluids have higher thermal efficiency as compared to base fluid. Some fluids have poor thermal conductivity like, water, air and ethylene glycol and oil. Thus, the thermal efficiency of the work can be increased by inserting the nanoparticles into base fluid. Furthermore, the nanoparticles can be used to enhanced the cooling rate of the system due to higher thermal conductivity. In this investigation, the magnetohydodynamics convective flow phenomenon under the consideration of different nanofluids inside a triangular porous conduit will investigated. For the better understanding of heat transfer characteristics, the thermal radiation and heat generation (or absorption) will also incorporated. We will impose constant and variable temperature on the left inclined wall to analyze the heat transfer mechanism. Furthermore, the heat transfer rate will also be analyzed by considering different nanoparticles. The robust numerical scheme namely the finite element method has been selected to simulate the nonlinear complex flow equations based on iterative scheme. In this technique, at the first stage the penalty method is employed for the purpose of the elimination of pressure from the equations of motion. After that the developed the system in the absence of pressure term is solved. To simulate the problem the value of penalty parameter is chosen 10−7. The contours of stream function and temperature distribution are displayed for several values of physical parameters. Furthermore, the variations of important quantity known as an average heat transfer rate are displayed through bar charts. For constant heating case the aluminum nano particles are the best choice to enhance the heat transfer rate in the system. Moreover, the magnitude of the stream function rises against the radiation and Rayleigh number. Furthermore, the conduction mode of heat transfer is achieved via thermal radiation parameter. The applications of the given study can be found in various industrial processes like, cooling of electronic devices, cooling of house and commercial buildings, cooling of microelectronics, cancer therapy, vehicle thermal management, and heat exchangers.